Number of ATP molecules formed in anaerobic glycolysis ?

**Core Concept**
Anaerobic glycolysis is a metabolic pathway that converts glucose into pyruvate in the absence of oxygen, generating a small amount of ATP and NADH. This process is crucial for cellular energy production under low oxygen conditions.

**Why the Correct Answer is Right**
In anaerobic glycolysis, one glucose molecule is broken down into two pyruvate molecules, resulting in a net gain of 2 ATP molecules. This is achieved through the conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate, which is coupled to the generation of ATP. The reaction is catalyzed by the enzyme phosphoglycerate kinase.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because anaerobic glycolysis does not produce ATP through oxidative phosphorylation, which is a process that requires oxygen.
* **Option B:** This option is incorrect because anaerobic glycolysis generates a net gain of 2 ATP molecules, not 4.
* **Option C:** This option is incorrect because anaerobic glycolysis produces NADH as a byproduct, but the question specifically asks about ATP molecules formed.

**Clinical Pearl / High-Yield Fact**
Anaerobic glycolysis is an essential mechanism for energy production in cells under hypoxic conditions, such as in ischemic tissues or during intense exercise. Understanding the yield of ATP in anaerobic glycolysis is crucial for appreciating the limitations of cellular energy production in the absence of oxygen.

**Correct Answer: B. 2**